Cathode for audions



S. S. (URRISI.

CATHODE FOR AUDIONS.

APPLICAHON FILED JULY 0, 191a Patented Feb. 15, 1921.

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Specification of Letters Patent.

Patented Feb. 15, 1921.

Application filed July 10, 1918. Serial No. 244,150.

To all whom it may concern Be it known that I, SAMUEL S. Toamsi, a citizen of the United States, residing at Philadelphia, in the county of Philadelphia, State of Pennsylvania, have invented new and useful Improvements in Cathodes for Audions, of which the following is a specification.

This invention relates to the improvement on the present type of filament cathodes used in audions, amplifiers and all other instruments where a filament is used as cathode for the emission of electrons.

A few recognized defects in the present type of filament cathodes consist of its small exposed surface and its duration of life, Which although sometimes lasting a reason able length of time, eventually must burn put, thus making the whole instrument useess.

The object of this invention is to eliminate the filament cathode, substituting for it a cathode which is constructed so as to contain in its inside a heating coil, heating the cathode walls; causing them to emit electrons, and which heating coil is renewable from the outside of the instrument. Another object of this invention is to provide a cathode which has a larger surface.

Figure 1, is a view in elevation, partly sectioned, illustratin the application of the cathode embodying eatures of the present invention to an audion, and

Fig. 2, is a similar view of the cathode detached.

In the accompanying drawings Fig. 2 re resents an enlarged form of this cathode w ich is made of metal preferably nickel, cylindrical shape, airti ht, with a thin cap, A, also of nickel whic is platinum plated both inside and outside. and coveredon the outside walls with an oxid to facilitate and intensifyelectron discharges. The cap A is coated, internally and externally considered, upon the emitting portion only with platinum. That portion of cap A exposed to vacuum within a lamp pro or is coated with oxid. Substantially mi way of the length of the cathode is an annular recessed portion having welded thereto an annulus G of platinum. A standard type of audion is so fitted with respect to the said recessed portion of the cathode that an air tight space is present around that part of the cathode above the part G.

Running through the whole length of this tube is a rod of mica, porcelain or any other heat resisting composition F wound on its tip with the heating coil 0 with leads E running down this rod to the outside of the tube making two connections J and M.

The rod F has a covering of thin mica sheet B and N to prevent the wires of the heat coil from coming into contact with the inner wall of the cathode A. The threaded cap L serves to prevent the rod F from slipping out.

The cathode connection I is through the binding post, soldered at H.

In the drawing Fig. 1 represents the mode of ad ting this tube to the audion; G being in while J and M are the heat coil terminals. I is a connection for the tube acting as the cathode.

What I claim is 1. A cathode and a heat coil wound upon a removable rod inolosed in the cathode renewable for heating the cathode.

2. A rod of heat resisting material having wound on it a heat coil to heat an electron emitting cathode and a cathode for housing said coil.

3. A cathode having its outer end closed, a heat coil and a thin sheet of heat resisting insulator to prevent the heat coil touching the metal walls of the cathode.

4. A cathode of the character stated comprising an elongated tube-like cap one end of which is positively closed. a rod removably mounted in said cathode, a heat coil wound upon said rod and an annular member of platinum applied to said cathode below the emitting portion of said cathode.

In witness whereof, I hereunto subscribe my name this 9th day of July, A. D. 1918.

WILLIAM J. JACKSON, Josnrn Tomusr. 

